Hypocholesterolemic effect of compounded freshwater clam protein hydrolysate and Gracilaria

The muscles of freshwater clam and whole Gracilaria powder (WG) were separately extracted using hot water. The residual meat was first freeze-dried, then hydrolysed at 50 °C by Protamex to obtain freshwater clam hydrolysate (PX5). The WG was separated into two fractions, designated as soluble (SDF) and insoluble dietary fibre (IDF). The in vitro bile acid-binding capacities and inhibition of micellar solubility of cholesterol were then investigated using the compounded PX5 and dietary fibre of WG or IDF. Assuming that bile acid binds to cholestyramine at 100%, the relative bile acid-bindings of PX5 and WG were 35.9% and 41.1%, respectively. Bile acid-binding of compounded PX5 and WG showed the best synergistic effect at a ratio of 1:3 (w/w) and relative bile acid-binding of 45.7%, significantly higher than PX5 and WG alone. After peptic digestion, the resulting inhibitions against cholesterol micelle formation in cholestyramine, PX5, WG and IDF were 97.6%, 18.5%, 30.8% and 49.3%, respectively.     

Hypocholesterolaemic effect of Bifidobacterium animalis subsp. lactis (Bb12) and trypsin casein hydrolysate

Hypercholesterolaemia is one of the most important risk factors in the development of cardiovascular disease. In this study, we report the in vitro potential of Bifidobacterium animalis subsp. lactis (Bb12) cultures and bovine casein hydrolysates formed by trypsin and Bb12 culture to reduce cholesterols levels. Cholesterol levels in vitro were reduced by up to 48% after incubation with Bb12 and up to 87% after incubation with trypsin hydrolysates, whereas unhydrolysed bovine casein did not affect cholesterol levels. Individual peptide fractions, obtained from size-exclusion chromatography, from casein hydrolysates formed by trypsin after a 48 h hydrolysis, reduced cholesterol levels by 2.7–50%. The molecular masses of these fractions, containing hypocholesterolaemic peptides, were below 1200 Da, as determined by LC-MS.     

Chemical compositions and nutritional value of Asian hard clam (Meretrix lusoria) from the coast of Andaman Sea

Chemical compositions and nutritive value of the edible portions including foot, mantle and viscera of Asian hard clam (Meretrix lusoria) harvested from the coast of Andaman Sea were determined. Proximate compositions varied with portions tested. Edible portions had moisture (76.23–84.22%) and protein (9.09–12.75%) as the major components. Carbohydrate (0.32–7.89%), fat (1.58–6.58%) and ash (1.23–2.58%) were also found at various levels, dependent upon portions. Myofibrillar proteins were observed as the major fraction in foot (40.54%) and mantle (31.65%), whilst non-protein nitrogen constituents were dominant in the viscera (36.85%). All portions contained a large amount of essential amino acids (167.66–187.63 mg/g sample), in which leucine (30.91–36.96 mg/g sample) and lysine (35.24–36.03 mg/g sample) were predominant. They were rich in polyunsaturated fatty acids (46.84–49.18% of total fatty acid) with high level of DHA (13.33–16.47 % of total fatty acids) and EPA (4.75–7.11% of total fatty acids). Cholesterol of 0.07–0.21% wet weight was detected. All portions were also rich in macro- (Na, K, Ca and Mg) and micro- (Fe, Zn, Cu and Cr) minerals. Therefore, Asian hard clam is an excellent source of several nutrients, which could be beneficial for the health of the consumers.     

In vitro model to correlate viscosity and bile acid-binding capacity of digested water-soluble and insoluble dietary fibres

Binding and excretion of bile acids in the small intestine by water-soluble and insoluble dietary fibres is one of the main mechanisms for their cholesterol-lowering effects. A model for the determination of the bile acid-binding capacity of dietary fibres was developed. The experimental set-up allowed to correlate the bile acid-binding capacities of different fibres with their viscosities after in vitro digestion. For cellulose, native oat fibre and psyllium fibres clear correlations between viscosity and bile acid-binding capacity could be observed, whereas for water-insoluble lupin fibre such a correlation did not exist. Heat-damaged oat fibre also showed bile acid-binding despite of significantly decreased viscosity. The data demonstrated that bile acid-binding of digested dietary fibres may not be solely based on their viscosity but may be influenced by additional binding forces.     

Gene dosage effect on starch structure studied using maize polygenic model containing ae and su1 mutant alleles

The aim of this work was to enhance our understanding on the gene dosage effect on starch structure. Two mutant alleles, ae and su1, were selected for this study. With regard to their genetic functions, ae and su1 mutations are at two opposite extremes; therefore ae and su1 constituted an ideal pair of mutant alleles for manipulating starch structures. A full set of dosage combinations of ae and su1 were constructed in the maize W64A inbred line, and matured kernels were subjected to starch structure analysis. Scanning electron microscopy showed that starch granule morphology was affected by high doses of ae and su1 alleles. X-ray powder diffraction showed that 3 doses of su1 were not able to change the crystalline pattern of starch, whereas 3 doses of ae transformed A-type pattern to B-type. Size-exclusion chromatography showed that homozygous ae, su1, and ae su1 led to drastic change of starch structure from that of non-mutant. In addition, starches from certain ae and su1 dosage combinations were different from those of homozygous genotypes. This study will lay further foundation towards genetic modification of starch for desirable functional properties in food.     

Effect of air-drying temperature on physico-chemical properties of dietary fibre and antioxidant capacity of orange (Citrus aurantium v. Canoneta) by-products

Dehydration promoted important modifications affecting both the physico-chemical properties of dietary fibre (DF) and the antioxidant capacity of orange by-products (peel and pulp remaining after juice extraction). The significance of such changes was largely dependent on the air-drying temperature used (from 30 °C to 90 °C). The major modifications on the DF components were observed when either extended drying periods, i.e. at lower temperatures, or elevated drying temperatures were applied. Dehydration around 50–60 °C apparently promoted the minor disruption of cell wall polymers, in particular of pectic substances. Pulp samples exhibited higher values of swelling (SW) and fat adsorption capacity (FAC) than those derived from orange peel. Although, significant decreases in water retention capacity (WRC), FAC and solubility values were detected for both by-products as the air-drying temperature increased. The antioxidant capacity associated to dehydrated citrus by-products was significantly higher for orange peel than for pulp samples. In general, the by-products studied proved to be quite resistant to the different heat treatments applied within the range of 40–70 °C. In overall, the study shows that, in order to preserve either the DF quality and/or the antioxidant capacity, air-drying temperature should be controlled since both types of compounds, DF components and antioxidants, might be degraded or modified either when extended drying periods and/or high drying temperatures are applied.     

Diversity of culturable microorganisms and occurrence of Listeria monocytogenes and Salmonella spp. in Tuber aestivum and Tuber melanosporum ascocarps

The aim of this study was to investigate the total mesophilic microorganisms, Pseudomonas genus, Enterobacteriaceae family, mold and yeast counts and the presence of Listeria monocytogenes and Salmonella spp on Tuber aestivum and Tuber melanosporum ascocarps. The results confirmed that the major percentage of the microorganisms, approximately 9.0 log ufc/g, were present in the peridium, the glebas of healthy truffles being practically free of microorganisms. The predominant microbial group was the Pseudomonas averaging 8.3 and 8.4 log cfu/g on T. aestivum and T. melanosporum whole ascocarps, respectively. The Enterobacteriaceae also achieved high populations, especially in T. aestivum truffles, with 6.3 log cfu/g. Molds and yeasts never exceeded 5.0 log cfu/g. The characterization of the isolates revealed that the fluorescens pseudomonads were the most prevalent. Raoultella terrigena and Enterobacter intermedius were the dominant Enterobacteriaceae. The identification of the yeast isolates revealed five species: Debaryomyces hansenii, Issatchenkia scutulata, Rhodotorula aurantiaca, Saccharomyces dairensis and Trichosporon beigelii subspecies A and B. The mold genera detected in both species of truffles were Aspergillus, Cladosporium, Penicillium and Fusarium, Trichoderma being present only in T. aestivum. L. monocytogenes was found in 10% of the samples of T. aestivum analysed but Salmonella spp. was not detected. Knowledge of the microbial population in terms of possible food borne and pathogen microorganisms is very useful for establishing successful disinfection and storage methods to prolong the shelf-life of ascocarps of T. aestivum and T. melanosporum.     

The inhibitory effect of Plectranthus barbatus and Plectranthus ecklonii leaves on the viability,glucosyltransferase activity and biofilm formation of Streptococcus sobrinus and Streptococcus mutans

Aqueous extracts of Plectranthus barbatus and Plectranthus ecklonii are traditionally used as anti-inflammatory and anti-fungal agents. The effect of these extracts and of its main component, rosmarinic acid, on the viability of the cariogenic bacteria, Streptococcus sobrinus and Streptococcus mutans, was determined by MIC and MBC. The influence of these extracts on the biofilm formation as well as on the inhibition of glucosyltransferase enzyme, produced by these species, was also analysed. Aqueous extracts of P. barbatus and P. ecklonii were stronger inhibitors than rosmarinic acid. MIC values of 3.8 and 4.7 mg/ml for S. sobrinus and 2.9 and 5.0 for S. mutans were obtained, while rosmarinic acid presented MIC values of 8.4 and 7.3 mg/ml. P. barbartus, P. ecklonii and rosmarinic acid presented MBC values of 9.5, 9.0 and 12.0 mg/ml for S. sobrinus, and 9.5, 10.0 and 12.5 mg/ml for S. mutans. The inhibition of biofilm formation by P. barbatus, P. ecklonii and rosmarinic acid presented IC₅₀ values of, respectively, 0.6, 1.0 and 3.1 mg/ml for S. sobrinus and 1.4 and 2.7 and 1.3 mg/ml for S. mutans. The glucosyltransferase inhibition activity by theses extracts and rosmarinic acid was calculated and IC₅₀ values presented were, respectively, 1.1, ca 1.2 and 2.1 mg/ml for S. sobrinus and 3.1, 1.6 and 3.9 mg/ml for S. mutans were obtained. These extracts may be useful in the prevention of dental carie.     

Short-term toxicological evaluation of Terminalia catappa, Pentaclethra macrophylla and Calophyllum inophyllum seed oils in rats

The purpose of this study was to evaluate the toxicological effects of feeding the oils of Calophyllum inophyllum, Pentaclethra macrophylla and Terminalia catappa to rats. The effects on physical appearance, feed intake, weight gain, plasma and tissue cholesterol and triacyglycerol levels in rats with 5% of the oils in normal rat feed were determined. Weekly monitoring of the rats showed good physical appearance and steady weight gain, with no mortality recorded for the period of the study. Haematological analysis of the rats indicated that they were not anaemic. Histopathotogical examination of the sections of the heart, liver, kidney and spleen revealed moderate (T. catappa oil) to severe fatty change and necrosis in the liver. Glomerulonephrotic changes in the kidneys of rats fed with T. catappa oil were moderate, while it was severe in the group fed with P. macrophylla oil. Severe myocardiac necrosis as well as atherosclerotic clefts in vasa vasori was observed in the vasa vasori of the hearts of rats fed with P. macrophylla oil. This change was moderate in the heart of rats fed with C. inophyllum, while no such observation was made in the group fed with T. catappa oil. There was a significant difference in the plasma cholesterol levels of the rats fed with C. inophyllum and T. catappa oils when compared with the control rats, while those fed with P. macrophylla oil had no significant difference. The oil of T. catappa appears more suitable for consumption than the oils from C. inophyllum and P. macrophylla. Fatty acid analysis of the oils showed that they have high amounts of unsaturated fatty acids with linoleic and oleic acids as the major ones.     

Effects of Amelanchier fruit isolates on cyclooxygenase enzymes and lipid peroxidation

Bioassay-directed isolation and purification of the ethyl acetate and methanol extracts of Amelanchier canadensis resulted in 1,3-dilinoleoyl 2-olein (1), 1,3-dioleoyl 2-linolein (2), 5-hydroxymethyl-2-furfural (3), 5-(sorbitoloxymethyl)-furan-2-carboxaldehyde (4), 5-(mannitoloxymethyl)-furan-2-carboxaldehyde (5), and 5-(α-d-glucopyranosyloxymethyl) furan-2-carboxaldehyde (6). Four compounds, oleanolic acid (7), ursolic acid (8), kaempferol-3-O-α-l-rhamnopyranosyl (1 ← 2) rhamnopyranoside (9), and kaempferol-3-O-α-l-rhamnopyranoside (10) were isolated from the ethyl acetate extract of fresh fruits of Amelanchier arborea. The compounds were isolated and purified by various chromatographic techniques and characterized by NMR and GC/MS methods. The isolated compounds inhibited lipid peroxidation (by 85%) at 100 ppm when compared to 89%, 87%, and 98% for the commercial antioxidants butylated hydroxy anisole (BHA), butylated hydroxytoluene (BHT), and tert-butylhydroxyquinone (TBHQ) at 1.67, 2.2, and 1.67 ppm, respectively. Although not selective, some of these compounds inhibited cyclooxygenase (COX)-1 and -2 enzymes. Compounds 3–6 were isolated for the first time from A. canadensis and compounds 7–10 were isolated for the first time from A. arborea fruits.     

Optimization of the production of Momordica charantia L. Var. abbreviata Ser. protein hydrolysates with hypoglycemic effect using Alcalase

Momordica charantia L. Var. abbreviata Ser. protein was hydrolyzed using six different proteases. The results showed Alcalase 2.4L to have the best hydrolyzing capacity, followed by Pancreatin. In addition, Alcalase hydrolysate had stronger hypoglycemic effect than that of Pancreatin hydrolysate at the same dose. Alcalase was chosen to produce M. charantia L. Var. abbreviata Ser. protein hydrolysates (MCPHs) with hypoglycemic effect. Response surface methodology (RSM) was applied to optimize the hydrolysis conditions using Alcalase. Model equation was proposed with regard to the effect of enzyme/substrate ratio, pH and temperature. The optimum values for enzyme/substrate ratio, pH and temperature were found to be 2.37%, 9.2 and 57 °C respectively.     

Short communication: Antimicrobial effect of lactoferrin and its amidated and pepsin-digested derivatives against Salmonella Enteritidis and Pseudomonas fluorescens

The antimicrobial effect of bovine lactoferrin (LF) and its amidated and pepsin-digested derivatives, at concentrations varying from 0.25 to 20 mg/mL, against 3 Salmonella Enteritidis strains and 3 Pseudomonas fluorescens strains was investigated. Lactoferrin showed its maximum antimicrobial effect at 10 mg/mL against the 3 Salmonella strains, with reductions ranging from 1.3 to 2.0 log units, and the 3 Pseudomonas strains, with reductions ranging from 1.8 to 5.4 log units. In the case of amidated LF, the maximum effect on the 3 Salmonella strains was recorded at 0.25 mg/mL, with reductions in the range of 0.8 to 1.2 log units, whereas it was recorded at 1 mg/mL for the 3 Pseudomonas strains, with reductions in the range of 4.4 to 6.0 log units. Pepsin-digested LF showed its maximum antimicrobial effect at 1 mg/mL against the 3 Salmonella strains, with reductions ranging from 2.6 to 3.4 log units, and at 20 mg/mL against the 3 Pseudomonas strains, with reductions ranging from 4.5 to 5.4 log units. It is worth noting the pronounced effect (reductions exceeding 2.5 log units) of a low (1 mg/mL) concentration of pepsin-digested LF, which is naturally formed in the gastrointestinal tract, on Salmonella and Pseudomonas strains. A highly significant inverse correlation was found between capsule polysaccharide levels of bacterial strains and their lethality in the presence of different concentrations of amidated lactoferrin.     

Emulsifying and foaming properties of Phaseolus vulgaris and coccineus proteins

Protein isolates from two Phaseolus cultivars, common bean (Phaseolus vulgaris L.) and scarlet runner bean (Phaseolus coccineus L.), were prepared by wet extraction methods (isoelectric precipitation – 4000 rpm, ultrafiltration, extraction with NaCl 2%, and isoelectric precipitation – 9900 rpm). The protein isolates were characterized by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and then evaluated for their solubility. The emulsion stability of emulsions produced at pH 7.0 and 5.5 with 1% or 2% or 3% w/v protein isolate was evaluated by average droplet size diameter, viscosity and creaming measurements. Emulsions with 1% protein content were unstable through storage. Emulsions with 3% w/v protein isolate concentration, extracted by ultrafiltration at pH 5.5 from both cultivars, were flocculated; this was more pronounced for coccineus isolates. The foaming properties, for the respective foams, were investigated. Foams with 1% w/v protein showed little foaming ability Ultrafiltration isolates produced more foam, which was especially stable at pH 5.5.     

Angiotensin converting enzyme (ACE) inhibitory,antihypertensive and antihyperlipidaemic activities of protein hydrolysates from Rhopilema esculentum

Angiotensin-converting enzyme (ACE) inhibitory, antihypertensive and antihyperlipidaemic activities of protein hydrolysates (RPH) from the jellyfish Rhopilema esculentum were investigated. R. esculentum was hydrolysed sequentially with pepsin and papain, and then the hydrolysate was ultrafiltered with a 2000 Da cut-off membrane. It was found that RPH contained high levels of Gly, Glu, Pro, Asp and Ala, having potential ACE inhibitory activity in vitro with an IC₅₀ of 1.28 mg/ml. It was also found that systolic blood pressure was reduced markedly in spontaneously hypertensive rats after single and chronic oral administration of RPH, indicating that RPH had an antihypertensive effect. In addition, oral administration of RPH decreased total serum cholesterol and triglyceride, and increased high-density lipoprotein cholesterol in rats fed with high-fat diet. These results indicate that RPH may prove to be a promising functional food for the prevention and treatment of hypertension and hyperlipidaemia.     

Hyperspectral transmittance imaging of the shell-free cooked clam Mulinia edulis for parasite detection

The clam Mulinia edulis is occasionally infected by the parasite Edotea magellanica. In this paper the normalized optical transmittance of the clam and its parasite have been disclosed for the first time using a hyperspectral imaging system. It has been identified that, in the spectral band of 600–950 nm, the normalized optical transmittance of clam’s mantle cavity changes in the presence or absence of the parasite. This relative change in the normalized optical transmittance has been used as an effective spectral feature for designing parasite detectors. As a proof of concept two detectors have been designed. The first detector, which relies on all the hyperspectral information, achieved a perfect detection accuracy in identifying parasite-infected clams. The second detector, which is based on a reduced number of hyperspectral bands, achieved an 85% detection accuracy. These results provide insights on the fundamental trade-off between detection accuracy and the amount of hyperspectral information for parasite detection in clams.     

Short communication: Biofilm production characterization of mecA and mecC methicillin-resistant Staphylococcus aureus isolated from bovine milk in Great Britain

Staphylococcus aureus is an important cause of contagious intramammary infection in dairy cattle, and the ability to produce biofilm is considered to be an important virulence property in the pathogenesis of mastitis. The aim of this study was to characterize the biofilm formation capacity of methicillin-resistant Staph. aureus (MRSA), encoding mecA or mecC, isolated from bulk tank milk in Great Britain. For this purpose, 20 MRSA isolates were grown on microtiter plates to determine the biofilm production. Moreover, the spa-typing and the presence of the intercellular adhesion genes icaA and icaD were analyzed by PCR. All MRSA isolates tested belonged to 9 spa-types and were PCR-positive for the ica genes; 10 of them (50%) produced biofilm in the microtiter plate assay. This is also the first demonstration of biofilm production by mecC MRSA.